Will my car run better without the catalytic converter?

Answer 1

Bad Idea & IllegalFirst of all, it is against Federal law to do this. There is a very heavy fine and possible imprisonment for violating this law. Furthermore it is illegal to sell a vehicle with tampered emission systems. So if you trade it in, at a dealer, on a new car, they will probably report the violation to the EPA.

If you sell it to a private individual, they would be obligated, under the law, to report it. I guess it's safe to assume the state you live in does not have emission testing, I say that because there would be no way this vehicle would pass inspection.

Now, with that said, you can do whatever you want with the car. But by law I can't help you tamper or modify the emission systems in any way.

The computer will see the missing catalytic converter, throw a DTC and alert the driver. A HO2S can not be left unplugged because the computer will see an open circuit, throw a DTC and alert the driver. The HO2S can not be bypassed. The computer will see it as a short , no pulsing signal and throw a DTC and Trigger the MIL light on the dashboard.

If the computer detects any missing inputs, it will use a set of values stored in memory. These values are not optimal so mileage will DECREASE. So if you disconnect HO2 and somehow keep the MIL from coming on, the computer will go to it's stored values and compute fuel mixture from that.

With no converters to burn off the fuel before it gets to the O2 sensors &

the cars ECU not knowing that the converters are missing, the cars ECU will

see the engine will be running rich. So the cars ECU will turn down the fuel

thinking the engine is rich, to get the fuel ratio in it's norm setting.

So now your engine is running lean.

I agree with the issue with OBDI/II vehicles which have post CAT O2 sensors. Cats are designed to burn excessive unburned fuel vapors after the combustion chamber so I don't see the benefit to run without them. If you have a modified engine that is port and or polished for more exhaust flow there are high-flow CATs available as an aftermarket option.

Of course converting from a OBD/ECU/DME fuel injected controlled engine to "old school" carberatered fuel deliver it wouldn't matter. Though if your county DMV requires smog then forget about it.

Cost wise and the pain of doing that to the cats will have to be thought about

before doing. You will have to change a lot!

Being now the engine is running lean, you will have to run 91+ to bring up

the less fuel used from being lean to be close to 87 in combustion.

Less of 91 = 87 or so in the speed of the fuel in combustion.

You would also have to "Cut back" your spark plugs to burn more fuel, use a colder plug. Also making a issue of fouling the plugs if not balanced right,

the cold of the plug, cut back and the higher 91 fuel.

More over you might have to take out your thermostat to get the engine to cool off in the 110 deg heat! 91 fuel does it's best but things will run close to lean. It's all touchy. The exhaust heat / fire is also going down the pipe now

making the pipe hotter. Those cats tend to do a 100% job of keeping the combustion from going down the pipe further.

The Ceramic core of the converter when ground up is really only like 8oz! And the funnel like shapes it has was always there so for saying it slows down your exhaust flow by having to fill in the void is sort of not there.

The louder noise from a open exhaust will do that.

So you might to keep a stock muffler.

That is really the quantum theory of running a car with no cats.

All because the fuel does not get burned off!

If you have a old car with one O2 sensor before the cats then all is ok!

Other than the heat in the exhaust pipe and noise slowing the flow!

And the law of the car. Once you do it it's your car for life till you fix it.

Is it worth doing? Not really over all!